Peerless: The broadcaster gets up close to a wandering albatross chick while filming Life in the Freezer in South Georgia in 1992

Honoured: The Queen presents Sir David with the Insignia of the Order of Merit, recognising exceptional achievements in the advancement of arts, learning, literature and science, in 2005

Fearless: Proving he is still challenging himself, Sir David abseiled down a 42ft wall at Cambridge University last month

Sir David joined the BBC after a short stint at a publishing company, a position that he took after leaving the Royal Navy in 1949.

However his now legendary documentaries nearly never happened - the young Attenborough was initially discouraged from appearing on screen because his bosses thought his teeth were too big for television.

His major break came in 1954, when he was brought in to front wildlife series Zoo Quest after the intended presenter fell ill on location. The series, which was broadcast until 1963, took British viewers into far-flung countries - and supercharged the young naturalist's career.

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In the decades since, Sir David has been behind some of the most successful documentary series in British television, including Life On Earth, The Living Planet, Planet Earth and Frozen Planet.

His work has inspired dozens of other TV presenters.

Springwatch star Michaela Strachan described the naturalist as 'a god of wildlife presenters'. She said: 'I think when you think of wildlife programmes and presenters, he's God, isn't he? He's up there and we are all really proud of him and have all been inspired by him.

'And he is unbelievably intelligent, not just on wildlife but on many other subjects as well. I don't know anybody that doesn't like David Attenborough. I know lots of people that don't like us but everyone loves him.'

Friend of the animals: Sir David with a chimpanzee and puckering up to Cocky the cockatoo at London Zoo

Personal touch: Sir David feeds a mother orangutan as her baby looks on in an intimate photograph taken in 1982

Beloved: Sir David joins the Queen as she delivers her Christmas Message in the Royal Mews at Buckingham Palace in December 1986

Natural world: Sir David discusses the habits of the vogelkop bowerbird while filming on location in Western New Guinea in 1995

Approachable: One fan brought her pet meerkat to meet Sir David at a book signing in 2008. Right, winning a BAFTA in 2009

Royal favourite: Sir David chats with Prince Charles at a dinner for The Prince's Rainforest Project in London in September 2008

Presenter Chris Packham, who is regarded by some as an heir to Sir David's throne, said: 'He told us stories, that's the great thing. You'd sit down and he would lead you through that. He would lead you, he would never lecture you.

'So he invited you into his story, which he wrote and he told and you believed everything that he said. And when you started listening at the beginning, by the time you'd got to the end you learned something.

'So you took something away from that and that was, I think, the great legacy of his early programmers. You went somewhere with someone you trusted. You learned a lot and it was a wholly enjoyable experience because you could sense that he was so passionate about it.'

Martin Hughes-Games said he had fond memories with the broadcaster, adding: 'I made a programme with David and it was about an earwig.

Recognition: Sir David with Terri Irwin, the widow of Steve Irwin, at the 2006 National Television Awards. Right, receiving an honourary degree from Oxford Brookes University in 2003

Full of life: Sir David Attenborough, centre, Harry Potter actor Daniel Ratcliffe, left, and Jonathan Ross with penguins in 2012

'It was just a half-hour programme about an earwig and David was absolutely fascinated by it. I think that is one of the secrets, he has enjoyed learning and discovering things all the way through his life.'

Welsh presenter Iolo Williams added: 'He's a fabulous communicator, bar none, and when he went to see Barack Obama it was as if Obama was in awe of him.'

Meanwhile, dozens of fans also took to Twitter to wish Sir David well on his milestone birthday. One wrote: 'Happy Birthday Sir David. Voice of my childhood. The wonders that he brought to the screen make me feel lucky to be alive. #Attenborough90'.

Another posted: 'Happy Birthday Sir David Attenborough! You're such a great inspiration in my life and many others; wishing you the best! #Attenborough90'.

The Duke of Cambridge were among those who paid tribute to Sir David in a special BBC programme tonight.

Prince William said it is fitting that Sir David and the Queen are celebrating their 90th birthdays just weeks apart as both are 'incredible national treasures'.

Tributes: Singer Ellie Goulding, Natural History Museum and London Zoo all wished Sir David a happy birthday

He said: 'There is something very calming and sort of warm about his programmes. There is something very reassuring about seeing David Attenborough on BBC One doing his documentaries. It is part of the national psyche now.

'He's a national treasure and it is very fitting that he is having his 90th birthday only a few weeks after the Queen. They are two incredible national treasures who have done so much over the years.'

David Cameron wished Sir David a happy birthday on behalf of the country, and said he had grown up watching and learning from the broadcaster.

'Your lifelong service has created the most extraordinary educational legacy,' he said. And even today you are pioneering the latest technologies.

'Britain is incredibly proud to have the greatest naturalist on the planet. For just as you treasure the world, so the world rightly treasures you.'

Fan favourite: Dozens of viewers also took to social media to pay tribute to Sir David as he celebrates this milestone